Bone implants

ABSTRACT

The present invention relates to an implant, to an instrument for implantation of the latter and to a method for manufacturing this implant which includes an elongated body (10) between a free end and a head (18) along a longitudinal axis on the one hand and turns (12) of at least one threading on at least one portion of said body (10) in proximity to the free end, along the longitudinal axis on the other hand, characterized in that the body (10) includes a longitudinal internal conduit (11) in at least one portion to along the longitudinal axis, obtained by at least one first central machining operation parallel to the longitudinal axis and at least one second machining operation in a so-called transverse plane, not parallel to the longitudinal axis and crossing the wall of the body (10) as far as the longitudinal internal conduit (11) by making windows (15) communicating between said longitudinal internal conduit (11) and the outside of the body (10).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of bone implants, inparticular spinal implants, for example for arthrodesis of the twovertebral structures. The present invention more particularly relates tospinal implants, notably so called “facet” implants intended to beimplanted between the articular facets of the vertebrae (so-called“intra-facet” implants) and/or implanted through these articular facetsof the vertebrae (so-called “trans-facet” implants). Various embodimentsof the present application are also adapted to implantation in vertebralpedicles (so-called “pedicular” implants) or at the sacro-iliac joint orin various types of bone structures, either spinal or not, although thecharacteristics of the implants described in the present applicationmake them particularly useful for their use in the rachis.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

A problem in the field of implants relates to bone growth and notablyarthrodesis, i.e. the bone merging of two structures, such as forexample vertebrae. Indeed, it is sometimes sought to obtain merging ofat least two vertebrae for example when at least one of their adjacentintervertebral discs is lesioned. Various arthrodesis techniques areknown from the prior art, based on various types of implants such as forexample intersomatic cages (or arthrodesis cages) inserted in the placeof a disc in order to promote bone growth, or arthrodesis platesattached on both vertebrae in order to immobilize them and allowarthrodesis, or further osteosynthesis or arthrodesis rods, used forimmobilizing the vertebrae, to which they are generally connectedthrough pedicular screws or hooks, or finally inter-spinal implantsinserted between the spines of the vertebrae (or “spineous apophyses”)for immobilizing them and thereby facilitating merging. These types ofimplants aim at finding an answer to a problem known in the field whichis to stabilize the vertebral level to be treated. Solutions are alsoknown, notably at the lumbar and sacral level, using facet implantsallowing such stabilization, by attaching the articular facets with thepurpose of obtaining merging. For example, implants are known from theprior art, such as for example from patent FR2726171B1, in the form of ahollow cylinder provided with threading for screwing bones, forming ascrew in which a conduit and grooves are made in order to provide agrafting space allowing the insertion of tissue or bone substitute orcement for facilitating the merging of the structures in which the screwis implanted.

It will be noted that vertebral articular apophyses (or articularprocesses or pedicular facets) are designated here by the term of“articular facet”, since each vertebra is jointed with the one above andbelow through articular facets which are posterior and the invention isuseful for treating these articular facets, but it is possible tooptionally use various embodiments on other structures, notablyvertebral structures, such as for example costal or sacro-illiac facetsif need be. Articular apophyses protrude above and below the base oftransverse apophyses of the vertebrae, behind the pedicles. At thelumbar level for example, the upper articular apophyses are separatedfrom each other by a more considerable distance than that whichseparates the lower two. The articular facets which they support havethe shape of a vertical gutter, the concavity of which faces rearwardsand inwards, a gutter in which will be placed the lower articularapophyses, which have a convex articular surface in the oppositedirection, i.e. forwards and outwards. The lower articular apophysesprovide a convex articular surface in the form of a cylinder segment,which faces outwards and slightly forwards. This surface slides in theconcavity of the upper articular apophysis of the vertebra locatedbelow. These structures are therefore important for the stability of thevertebrae one on the other and it will moreover be noted that the bonedeficit (or “lysis”) of the isthmuses (or “pars inierarticularis”)located at their base is often responsible for spondilolysthesis (thesliding of a vertebra relatively to the other adjacent ones) whichgenerally lead to degeneration of intervertebral discs. When it issought to achieve vertebral arthrodesis, it is therefore sometimesdesirable to use a facet implant for attaching the lower articularapophyses of a vertebra to the upper articular apophyses of the adjacentvertebra. These facet implants may either be “inter-facet” implants, i.ethey are inserted between the articular surfaces, or “trans-facet”implants, i.e. they are inserted through the articular apophyses forattaching the articular surfaces together. Inter-facet implants aregenerally set into place in the articular joint by identifying theapproach axis and for example by positioning a broach used as a guidefor the implant, which is often cannulated (i.e. hollow). A problem inthe field relates to the solidity since it is desirable to guarantee theintegrity of the implant in spite of its small size and its oftenrecessed layout.

A problem relating to implants in general, in particular spinal implantsand notably facet implants, relates to the stability of the implant. Itis required that an implant be stable in its implantation site, inparticular when arthrodesis is desired since the latter should takeplace in a relative position of the elements of the rachis, which isoptimum. Stabilization and/or locking of the implant is(are) thereforeoften preferable. Another general problem relates to the ease and/or therapidity of the implantation. Further, it is generally desired that theimplants may be implanted with minimum invasiveness, i.e. it is soughtto limit the size of the incisions and of the damages on the surroundingtissues. Percutaneous solutions or only requiring a few millimeters ofincision (for example 2 to 40 mm) are often sought. Further, it isgenerally desirable to limit resorting to imaging in order to avoidexposing the patients to rays.

Intra-facet implants, often accompanied by other problems such that, forexample, the requirement of providing the graft or bone substitute orcement for facilitating the merging, for example by means of thepresence of a grafting chamber in the implant, in spite of its smallsize, and by maintaining sufficient rigidity of the implant in order tosupport the forces between both fixed facets. Further, it is generallydesirable to tap, clean out or sharpen the articular surfaces, forexample in order to remove cartilage and /or promote bone growth.

Transfacet implants, which often provide the advantages of being simple,being able to be used percutaneously and allowing compression ofarticular facets against each other, are often accompanied by otherproblems such as for example, the lack of sharpening, cleaning ortapping of the articular joints, which limits the bone growth rate.These implants generally include at least one implanted screw with anaim through articular surfaces (transfacet). They are generally alsoguided by a broach but they generally require that the bone beperforated beforehand, often percutaneously by means of a bit. It ispossible to tap the bone around the broach in order to screw in theimplant (often “cannulated”, i.e. hollow and slipped around the broach)which generally includes a bone thread (e.g., a threading adapted forscrewing into bone tissue), for example for not risking any fracturingof the facets during the setting into place. Finally, it is generallydesirable that these implants include a stabilization means (of eitherone of the facet or both facets) and /or a compression and/or lockingmeans and/or bone supporting means which will spread the loads over atleast one of the facets (notably the posterior facet) at the end of thescrewing.

The diversity of the problems, notably of those discussed above, isgenerally accompanied by the problem that a same implant cannot beequally used as a transfacet implant and as an interfacet implant, whichforces the provision of various types of implants and instruments.

In this context, it is interesting to propose a solution with which itis possible to efficiently provide an answer to said at least oneportion of these problems.

GENERAL DESCRIPTION OF THE INVENTION

The object of the present invention is to overcome certain drawbacks ofthe prior art by proposing a bone implant, in particular intended forimplantation at articular facets, further allowing stable, easy andrapid implantation.

This aim is achieved by a bone implant including, on the one hand, anelongated body between a free end and a head, along a longitudinal axisand, on the other hand, turns of at least one threading, on at least oneportion of said body in proximity to the free end along the longitudinalaxis, characterized in that the body includes a longitudinal internalconduit, on at least one portion along the longitudinal axis, obtainedby at least one first central machining parallel to the longitudinalaxis, and at least one second machining in a plane, a so calledtransverse plane, not parallel to the longitudinal axis, and crossingthe walls of the body as far as the longitudinal internal conduit bymaking windows communicating between said longitudinal internal conduitand the outside of the body.

Advantageously, these windows can be made so that the size of theimplant transversely to the longitudinal axis is locally reduced.

In addition, these windows can advantageously be made so as to preserveat least one portion of said turns and the wall of the body behind theturns, and by preserving a non-machined portion on the perimeter of saidbody.

This aim is also achieved by a bone implant including, on the one hand,an elongated body between a free end and a head, along a longitudinalaxis and, on the other hand, turns of at least one threading, on atleast one portion of said body in proximity to the free end along thelongitudinal axis, characterized in that, on the one hand, the bodyincludes a longitudinal internal conduit on at least one portion alongthe longitudinal axis and windows communicating between saidlongitudinal internal conduit and the outside of the body and, on theother hand, said windows have at least one sharpened outer edge.

This aim is also achieved by a bone implant including, on the one hand,an elongated body between a free end and a head, along a longitudinalaxis and, on the other hand, turns of at least one threading, on atleast one portion of said body in proximity to the free end along thelongitudinal axis, characterized in that, on the one hand, the bodyincludes a longitudinal internal conduit on at least one portion alongthe longitudinal axis and windows communicating between saidlongitudinal internal conduit and the outside of the body and, on theother hand, the head of the implant is provided with stabilization meansof the implant, intended to bear upon the bone tissue around said head.

This type of solutions have the advantage to allow a use as either atransfacet implant or as an interfacet implant, for example thanks tothe fact that the implant offers a large bony graft space in itsinternal conduit and/or that the bone will be of the for example by thefact that the implants provides a wide space for bone grafting in itsinternal conduit and/or that the bone will be sharpened or edged by thepassage of the implant and/or that the stability of the implant isimproved relatively to the known solutions.

According to another feature, said free end of the body isself-drilling.

According to another feature, said body is substantially cylindrical.

According to another feature, said body is substantially conical offrusto-conical.

According to another feature, the perimeter of said threading issubstantially cylindrical in spite of the conical or frusto-conicalshape of the body.

According to another feature, said windows are aligned with each otheralong a longitudinal axis.

According to another feature, said windows are shifted relatively toeach other along the longitudinal axis.

According to another feature, said windows are flared so that they haveat least one sharpened outer edge.

According to another feature, said head of the implants closes thelongitudinal internal conduit or includes means for closing thelongitudinal internal conduit.

According to another feature, said thread has a variable pitch becomingshorter in the direction of the heed.

According to another feature, said body is provided with several threadswith different pitches, the pitch of a thread located on the side of thefree end being of a larger size than the adjacent thread located on theside of the head.

According to another feature, said head of the implant is provided withstabilization means of the implant, intended to bear upon the bonetissue around said head.

According to another feature, said stabilization means include at leastone stabilization element forming a kind of staple comprising at leasttwo rods substantially parallel to the longitudinal axis and able topenetrate the tissue around the head and optionally a portion of saidbody in proximity to said head.

According to another feature, said rods of the stabilization elementhave a pointed free end.

According to another feature, said rods are connected together through aring making the stabilization element able to be mounted on said head.

According to another feature, said head includes at least two notchesable to receive said rods or shoulders positioned along said rods inorder to maintain them at a distance from the body.

According to another feature, said stabilization means include at leastone bell-shaped stabilization element mounted on the head and theperimeter of which is intended to bear upon the bone tissues surroundingthe head.

According to another feature, said bell includes at least one tip ortooth on its perimeter for facilitating bone anchoring.

According to another feature, said bell is mounted secured to the head.

According to another feature, said bell is movably mounted on said head.

According to another feature, said head has a peripheral lower surfacewith the shape of a spherical portion and mating an internal uppersurface of said bell thereby jointed on the head of the implant.

According to another feature, said stabilization means include at leastone plate mounted around the head and provided at least with one passageable to receive a stabilization element, a so-called anchor, with ashape of the plate able be anchored in the bone tissue around the head.

According to another feature, said anchor includes a pointed end and/orsharpened end intended to penetrate the bone tissue.

According to another feature, said anchor includes an end provided withat least one abutment intended to come into contact with said plate andlimit the penetration of the anchor onto the bone tissue.

According to another feature, said anchor is formed with a substantiallyplanar plate.

According to another feature, said anchor is formed with a substantiallycurved plate.

According to another feature, said anchor and said passage are laid outfor inserting the anchor along an oblique axis relatively to thelongitudinal axis, so that the anchor is oriented from the centertowards the periphery of the implant upon insertion.

According to another feature, the stabilization means include at leastone stabilization element in the form of a jaw comprising two curvedbits each comprising a free end and jointed together by two jointsseparated from each other by a space substantially equal to the size ofthe head so that the jaw may be mounted around the head and the bits maycome into contact with the bone tissues around the body of the implant.

According to another feature, the bits of said jaw include on theirconcave face, at least one catch for stabilizing them against the bonetissue.

According to another feature, the free end of the bits includes at leastone chamfer facilitating the opening of the jaw upon inserting theimplant into the bone tissue.

According to another feature, stabilization means include locking meansbearing upon the stabilization element for maintaining it pressedagainst the bone tissue.

According to another feature, at least one portion of said widows areseparated by at least two turns without any windows.

According to another feature, at least one portion of said windows aremade on several turns.

According to another feature, at least one portion of said windows aremade between said turns.

DESCRIPTION OF THE ILLUSTRATIVE FIGURES

Other particularities and advantages of the present invention willbecome more clearly apparent upon reading the description hereafter,made with reference to the appended drawings, wherein:

FIGS. 1A, 1B and 1C represent respective, front and profile views,respectively of an implant according to various embodiments, FIG. 1Dillustrates a sectional view along the sectional plane 1D-1D of FIG. 1C,

FIGS. 2A and 2D illustrate perspective views of an implant according tovarious embodiments and FIGS. 2B and 2C illustrate perspective views, ofa locking means and of a stabilization element, respectively, accordingto various embodiments,

FIG. 3A illustrates a perspective view of an implant provided withstabilizing and locking means according to various embodiments, FIGS.3B, 3C and 3F illustrate perspective, profile and top views,respectively of an implant body according to various embodiments andFIGS. 3D and 3E illustrate perspective views of a stabilization elementand of a locking means, respectively, according to various embodiments,

FIG. 4A represents a perspective view of an implant-holder retaining animplant according to various embodiments and FIG. 4B illustrates anenlargement of this implant-holder at its portion retaining the implant,

FIGS. 5A and 5B illustrate profile and sectional views respectivelyalong the sectional plane 5B-5B of FIG. 5A, of an implant-holderretaining an implant according to various embodiments and FIGS. 5C and5D illustrate enlargements of the figures, notably of FIGS. 5A and 5B.

FIGS. 6A, 6B and 6C illustrate perspective, face and profile viewsrespectively of an implant according to various embodiments, FIG. 6Dillustrates a sectional view along the sectional plane 6D-6D of FIG. 6C,

FIGS. 7A, 7B and 7C illustrate perspective views of a locking means, ofa stabilization element and of an implant, respectively according tovarious embodiments,

FIGS. 8A and 8B illustrate profile and sectional views respectivelyalong the sectional plane 8B-8B of FIG. 8A, of an implant holderretaining an implant according to various embodiments and FIGS. 8C and8D illustrate enlargements of the figures, FIGS. 8A and 8B respectively,

FIGS. 9A and 9B illustrate perspective and profile views respectively ofan implant according to various embodiments and FIG. 9C illustrate asectional view along a sectional plane 9C-9C of FIG. 9B,

FIG. 10A illustrates a perspective view of an implant-holder retainingan implant according to various embodiments and FIG. 10B illustrates anenlargement of this implant-holder at its portion retaining the implant,

FIGS. 11A and 11B illustrate profile and sectional views respectively,along the sectional plane 11B-11B of FIG. 11A of an implant-holderretaining an implant according to various embodiments and FIG. 11Cillustrates an enlargement of FIG. 11B,

FIGS. 12A and 12B illustrate perspective and profile views respectivelyof an implant according to various embodiments and FIG. 12C illustratesa sectional view along the sectional plane 12C-12C of FIG. 12B,

FIGS. 13A and 13B illustrate profile and sectional views, respectively,along the sectional plane 13B-13B of FIG. 13A, of an implant accordingto various embodiments,

FIGS. 14A and 14B illustrate profile and sectional views, respectively,along the sectional plane 14B-14B of FIG. 14A of an implant according tovarious embodiments,

FIGS. 15A and 15B illustrate profile and sectional views, respectivelyis along the sectional plane 15B-15B of FIG. 15A, of an implantaccording to various embodiments,

FIGS. 16A and 16B illustrate profile and sectional views, respectively,along the sectional plane 16B-16B of FIG. 16A, of an implant accordingto various embodiments,

FIG. 17A illustrate a perspective view of an implant-holder according tovarious embodiments and FIG. 17B illustrates an enlargement of thisimplant-holder at its portion indented to retain the implant,

FIGS. 18A and 18B represent profile and sectional views, respectively,along the sectional plane 18B-18B of FIG. 18A, of an implant-holderretaining an implant according to various embodiments and FIG. 18Cillustrates an enlargement of FIG. 18B,

FIGS. 19A and 19B illustrate perspective views of stabilization meansbefore and after assembling respectively, according to variousembodiments and FIG. 19C illustrates a perspective view of an implantprovided with such stabilization means,

FIG. 20A, illustrates a perspective view of an implant and of a portionof stabilization means according to various embodiments and FIGS. 20Band 20C illustrate perspective views of an implant provided withstabilization means and locking means, before and after assemblingrespectively, according to various embodiments,

FIGS. 21A and 21C illustrate perspective views of an implant and ofstabilization and locking means, before and after assembling,respectively, according to various embodiments and FIG. 21B illustratesa perspective view of such stabilization means,

FIGS. 22A, 22B and 22C illustrate front, profile and top views,respectively, of an implant according to various embodiments, FIG. 22Dillustrates a sectional view along the sectional plane 22D-22D of FIG.22B, FIGS. 22B, 22E, 22F and 22G illustrate front, profile and topviews, respectively, of an implant according to various embodiments,FIG. 22H illustrates a sectional view along the sectional plane 22H-22Hof FIG. 22F,

FIGS. 23A, 23B, 23C and 23E illustrate front, profile, top andperspective views, respectively, of an implant according to variousembodiments, FIG. 23D illustrates a sectional view along the sectionalplane 23D-23D of FIG. 23A,

FIGS. 24A and 24B illustrate profile and sectional views respectivelyalong the sectional plane 24B-24B of FIG. 24A, of an implant accordingto various embodiments,

FIGS. 25A and 25B illustrate profile and sectional views, respectively,along the sectional plane 25B-25B of FIG. 25A, of an implant accordingto various embodiments,

FIGS. 26A, 26B and 26C illustrate top, profile and sectional views,respectively, along the sectional plane 26C-26C of FIG. 26B, of animplant according to various embodiments,

FIGS. 27A, 27B and 27C illustrate top, profile and sectional views,respectively, along the sectional plane 27C-27C of FIG. 27B, of animplant according to various embodiments,

FIGS. 28A and 28B illustrate profile and sectional views, respectively,along the sectional plane 28B-28B of FIG. 28A, of an implant accordingto various embodiments,

FIGS. 29A and 29E illustrate profile views of an implant according todiverse embodiments, with a poly-axial locking in diverse positions,FIG. 29B represents a sectional view along the sectional plane 29B-29Bof FIG. 29A, FIGS. 29C and 29D illustrate views, respectively profileand sectional views along the sectional plane 29D-29D of FIG. 29C of animplant according to diverse embodiments,

FIGS. 30A and 30B illustrate views, respectively profile and sectionalviews along the sectional plane 30B-30B of FIG. 30A, of an implantaccording to diverse embodiments, FIGS. 30C and 30E illustrate profileviews of an implant according to diverse embodiments, with poly-axialstabilization in diverse positions, FIG. 30D illustrates a sectionalview along the sectional plane 30D-30D of FIG. 30C,

FIGS. 31A, 31C and 31D illustrate profile views of an implant accordingto diverse embodiments, with diverse configurations of its stabilizationmeans, FIGS. 31B and 31E illustrate sectional views, respectively alongthe sectional plane 31B-31B of FIG. 31A and along the sectional plane31E-31E of FIG. 31D,

FIGS. 32A and 32D illustrate views, respectively profile and frontviews, of an implant according to diverse embodiments, FIG. 32Billustrates a sectional view along the sectional plane 32B-32B of FIG.32A and FIG. 32C illustrates an enlargement of the surrounded portion inFIG. 32B,

FIGS. 33B and 33C represent views, respectively profile and front views,of an implant according to diverse embodiments, FIG. 33A illustrates asectional view along the sectional plane 33A-33A of FIG. 33B,

FIGS. 34B and 34C illustrate views, respectively profile and perspectiveviews, of two implants according to diverse embodiments, FIG. 34Aillustrates a sectional view along the sectional plane 34A-34A of FIG.34B,

FIG. 35A illustrates a profile view of an implant according to diverseembodiments and. FIG. 35B represents a sectional view along thesectional plane 35B-35B of FIG. 35A,

FIGS. 36A, 36B and 36C illustrate perspective views of an implantaccording to diverse embodiments, respectively before, during and afterassembling their locking means.

DESCRIPTION OF THE PREFFERED EMBODIMENTS OF THE INVENTION

The present invention relates to various embodiments of bone implantsand of instruments for implanting such implants. As mentioned in thepreamble of the present application, the invention may relate inparticular to spinal implants, for example for arthrodesis of twovertebral structures. The present application more particularly detailsspinal implants, notably so-called “facet” implants, intended to beimplanted between the articular facets of the vertebrae (so-called“intra-facet” implants) and/or implanted through these articular facetsof the vertebrae (so-called “trans-facet” implants). Various embodimentsof the present application are also adapted to an implantation invertebral pedicles (so called “pedicular” implants) or at the level ofthe sacro-illiac joint or in various types of bone structures, eitherspinal or not, although the characteristics of the implants described inthe present application make them particularly useful for their use inthe rachis. Further, the implants of various embodiments are obtained bya manufacturing method with which it is possible to obtain particularlyuseful implants, for example for providing at least an answer to part ofthe problem discussed in the present applications. Thus, variousembodiments may also relate to the method for manufacturing theseimplants.

Generally, the present invention preferably includes at least one boneimplant (1), the technical characteristics of which are detailedhereafter in various embodiments. Generally, in the case of animplantation at articular facets, it is preferred to use two implants soas to secure the two (left and right) facets which joint two adjacentvertebrae, but this use is of course not limiting.

Generally, the bone implant (1) includes a body (10) elongated between afree end and a head (18) along a longitudinal axis on the one hand and,turns (12) of at least one threading, on at least one portion of saidbody (10) in proximity to the free end, along the longitudinal axis onthe other hand. Further, the body (10) of the implant (1) preferablyincludes at least one longitudinal internal conduit (11) on at least oneportion of a body (10) along the longitudinal axis and windows (15) incommunication between said longitudinal internal conduit (11) and theoutside of the body (10).

In certain embodiments, this longitudinal internal conduit (11) isobtained by at least one first central machining operation parallel tothe longitudinal axis and at least one second machining operation in aso-called transverse plane, not parallel to the longitudinal axis andcrossing the walls of the body (10) as far as the longitudinal internalconduit (11) by making windows (15) in communication between saidlongitudinal internal conduit (11) and the outside of the body (10),Thus, the implant includes an internal conduit (11) which preserves atleast one portion of said turns (12) and the wall of the body behind theturns, and preserves non-machines portions thereof on the perimeter ofsaid body (10). Indeed, the transverse machining makes windows on onlycertain portions of the perimeter (certain angular sectors, radially)and leaves non-machined portions between the windows. It will be notedthat the transverse term is used here for referring to machining whichpreferably is only substantially transverse since it is achieved betweenthe turns, it is not in a perpendicular plane to the longitudinal axis,but rather parallel to the turns of the threading, so that it makeswindows along the same orientation as that of the turns. Nevertheless,in the case of a transverse machining over several turns, it is possibleto use machining perpendicularly to the longitudinal axis. Radial,tangential or oblique machinings are therefore used according to theconfigurations but the present description groups them under the term of“transverse”. Generally, regardless of how the internal conduit (11) isobtained, such non-machined portions on the perimeter of said body (10)are preserved so as to improve the solidity of the implant. It isunderstood that it is possible to preserve a variable number ofnon-machined portions depending on the number of transverse machiningoperations carried out. For example it is possible to provide twodiametrically opposite portions or three gradually distributed portionsaround the longitudinal axis (either regularly distributed or not) orfurther a multitude of portions for example as visible in FIGS. 1C, 22For 2D. In other words, it is possible to provide a transverse machiningevery 90°, but a machining every 60° or every 180° may be preferred forleaving greater non-machined portions and thereby preserve the solidityof the implant.

The terms of “head” and “free end” are used in the present inventionwith reference to the fact that the implant generally appears in theform of a screw, with a generally cylindrical or conical orfrusta-conical body (10), but these turns and these shapes of theimplant should not be considered as limiting. Diverse portions of theimplant are on the other hand designated in the present application bythe terms of “proximal” meaning “in proximity to the head”, or “distal”meaning “in proximity to the free end” or further “median” meaning“substantially in the middle between the two ends”, but it is clear thatthese terms are not either limiting and that the person skilled in theart will appreciate that the position of these portions may vary alongthe longitudinal axis. Further, the term of “appreciably” or“substantially” is used with reference to various features in order toindicate that they may be exactly as defined or be approximately asdefined. For example, the expression “a substantially planar shape”should be understood as designating a shape approximately planar sincethe person skilled in the art will be able to vary the exact shapeinsofar that it would keep a globally planar shape meeting the relevanttechnical requirements. Also, the present description may definefeatures without this specifying of approximation with the terms of“appreciably” or “substantially” but it will be clear for the personskilled in the art that this notion applies even in the absence of suchterms.

Further the term of “machining” is here used in a non-limiting way forreferring to the manufacturing of the implants and it is clear that thisterm in facts covers any type of manufacturing techniques, such as forexample, bores, drillings or milling operations, but alsoelectro-erosion or any type of technique giving the possibility ofmaking surfaces or accommodations on or in the implants. Further theterm of “transverse” is used for indicating that the second machiningoperation is in a plane not parallel to the longitudinal axis and tendsto indicate that it is perpendicular to the longitudinal axis, but theperson skilled in the art will notably understand because of the obliqueorientations of the turns of the threading, that this plane (which istherefore substantially transverse) is not necessarily perpendicular tothe longitudinal axis and will generally be rather Obliquely oriented,preferably parallel to the turns.

In certain embodiments, said body (10) is substantially cylindrical, asfor example visible in most of the figures, notably FIGS. 1C, 2D, 9C,etc. In other embodiments, said body (10) is substantially conical orfrusto-conical, as illustrated for example in FIGS. 22A, 22B, 22E, 22For 23A, 23B and 23E. This shape facilitates implantation of the bodysince the free (distal) is thinner than the proximal end. In some ofthese embodiments with a conical or frusta-conical body, the perimeterof said threading is substantially cylindrical in spite of the conicalor frusto-conical shape of the body (10), as for example illustrated inFIGS. 22A, 22B, 22E and 22F. This type of threading with a cylindricalperimeter on a frusto-conical body improves the stability of the implantsince the turns of the distal end will penetrate more deeply into thebone tissue.

Regardless of how the windows are obtained (longitudinal or transversemachining operations), aligning them or shifting them relatively to eachother may be preferred. Thus, in certain embodiment, said windows (15)are shifted relatively to each other along (or rather around) thelongitudinal axis, for example as illustrated in FIG. 2D, while in otherembodiments, said windows (15) are aligned with each other along thelongitudinal axis, for example as illustrated in FIG. 1C. It will benoted that it is also possible to provide a combination of thesearrangements, by providing aligned windows on one portion and shiftedwindows on another portion. When they are shifted relatively to eachother, it is generally preferred that a more proximal window be shiftedrelatively to a more distal window on the side which corresponds to thedirection of the screwing. Thus, for example with a threading orientedclockwise a proximal window will be shifted left relatively to a moredistal window, so as to improve sharpening of the bone or cartilagewhich may be gradually obtained with successive windows during screwing.

In the embodiments comprising a longitudinal internal conduit (11) anwindows (15) obtained by at least one first machining operation and atleast one second machining operation respectively. In these embodiments,the second machining, giving the possibility of obtaining the windows(15), preferably preserves the material of the body (10) behind theturns (12), as for example illustrated in FIGS. 1C, 1D, 2D, 7C and moreparticularly visible in FIGS. 12C, 26C or 27C. Thus, in particular inthe embodiments wherein the windows are obtained by a second machiningwhich is achieved along an orientation substantially transverse to thelongitudinal axis, these windows preserve the material behind the turns(since the first longitudinal machining has a diameter smaller than thatof the body at the turns). Thus, the person skilled in the artunderstands that the implant which results from this, is found to beimproved by the fact that it has turns which penetrate more deeply intothe tissue, as if they were larger, since the material around the turnshas been removed by the machine operation (thus reducing the residualwidth of the body) and that the pressure present in the surroundingtissues, in particular in the case of an implantation at an articularlevel, will ensure that the turn will sink into the bone more deeply.Further, the solidity of the implant is improved by means of thematerial preserved by the machining, while in the prior art, notablywhen the windows are made by a machining achieved uniquely along thelongitudinal axis of the implant, only the thread is preserved and theturns (12) are therefore alone in order to support the significantforces during and after the screwing. Thus, a stable and solid implantis obtained. Further, by making the windows by a second non-longitudinalmachining, it is possible to obtain (or optimize) an effect ofsharpening of the bone structures around the implant, during thescrewing, generally accompanied by a filling effect of the implantthrough these sharpened bone structures during the screwing. Indeed, bymaking windows (15) aligned with each other over several successiveturns (aligned along the longitudinal axis) and/or extending overseveral successive turns, a local reduction in the size of the perimeterof the implant is obtained (i.e., a local reduction in the diameter, ifthe implant is cylindrical or conical), like for example as visible bycomparing FIGS. 6C and 6D, 9B and 9C, 12B and 12C, 13A and 13B, 14A and14B or 24A and 24B, 25A and 25B, 26B and 26C, 2713 and 27C, 28A and 28B,but also as it may be inferred from a configuration such as that of FIG.35A, as detailed hereafter. Thus, during the screwing, the pressure ofthe surrounding bone structures leads to sinking of the turns into thebone tissue and the rotation of the implant causes sharpening of thebone against the edges of the windows (15), and often a “self-filling”of the implant by the thereby sharpened/cured tissues, In some of theseembodiments, the second machining operation may for example be carriedout tangentially to the perimeter of the body (10) resulting in windows(15) which are flared from the inside to the outside of the body (10),as (further) illustrated for example in FIGS. 1A, 2A, 3B, 2C, 6C, 6D,etc. However, alternatively, the second machining operation may becarried out substantially radially (or along an oblique axis between theradial orientation and the tangential orientation) so as to obtainwindows having at least one sharpened outer edge as detailed hereafter.Thus, certain embodiments relate to a bone implant (1) including anelongated body (10) between a free end and a head (18) on the one handalong a longitudinal axis and turns (12) of at least one threading, overat least one portion of said body (10) in proximity to the free end onthe other hand, along the longitudinal axis. This implant ischaracterized in that the body (10) includes a longitudinal internalconduit (11), over at least one portion along the longitudinal axis,obtained by at least one first machining (preferably central, but in allthe embodiments, this longitudinal machining is not necessarily central)parallel to the longitudinal axis and at least one second machining in aplane, a so called transverse plane, not parallel to the longitudinalaxis, and crossing the walls of the body (10) as far as the longitudinalinternal conduit (11) by making windows (15) communicating between saidlongitudinal internal conduit (11) and the outside of the body (10).Advantageously, this implant has windows (15) aligned with each otheralong the longitudinal axis and made between several successive turnsand/or extending over several turns, so that the size of the implanttransversely to the longitudinal axis (optionally excluding the turns,i.e, by only taking into account the turns) is locally reduced, whichpromotes sharpening of the tissues into which the implant is screwed andoptionally the automatic filling of the internal conduit (11) of theimplant with these tissues.

In certain embodiments, non-exclusive but however eventually independentof those with two non-parallel machining operations as defined above,said windows (15) of the bone implant (1) advantageously have at leastone sharpened outer edge. Indeed, regardless of how the conduit and thewindows are obtained, it may be useful to provide at least one sharpenedouter edge for the windows (15). In particular, it is generallypreferred that the sharpened edge be the one which first attacks thebone during the screwing of the implant, so that this sharpened edge maygradually dig into the bone (for example by cutting out shavings) duringthe screwing. Thus, when the windows (15) are obtained by a secondmachining operation, the latter may for example be achieved along radialor oblique axis as explained above, so as to obtain one sharpenedleading edge, as illustrated for example in FIGS. 23A and 23D (the rightouter edge on the window of FIG. 23D has a cutting edge which allowscutting out of the bones or of the cartilage). Also, if the windows areobtained, as in the prior art, by longitudinal machining operations, itis possible to provide the latter so as to make such a cutting edge, asillustrated for example in FIGS. 22C, 22D, 22E and 22F, which showillustrative and non-limiting examples of such machining operations (andmoreover shows the fact that a variable number of machining operationsmay be provided for making the windows). This type of layout with atleast one edge (preferably the leading edge) gives a possibility of atleast sharpening or scraping out the bone during the screwing, whichstimulates bone growth and stabilizes the implant, this also gives thepossibility, optionally, of automatically filling (at least partly) thelongitudinal internal conduit (11) during the screwing, which gives thepossibility of limiting the resorting to exogenous bone tissue or to asubstitute or to a cement, even if the latter may be used (additionallyor alternatively) in various embodiments. Indeed, diverse embodimentsprovide the use of exogenous bone tissue and/or of bone substituteand/or of cement in the implants, injected before or after (i.e., insitu) the setting into place of the implant, in order to facilitate bonegrowth.

On the other hand, in certain, non-exclusive embodiments but howeverindependent of those having two machining operations and/or with asharpened edge as defined above, said head (18) of the implant (1) isprovided with stabilization means (2, 3, 5) (e.g. compression, locking,supporting means) of the implant, intended to bear upon the bone tissuearound said head (18) (these stabilization means optionally comprisinglocking means for securing them on the implant). Various embodiments aredescribed hereafter for the stabilization means but the person skilledin the art will understand from this functional definition that theimplant is provided so that its head (which is generally the subsistingportion outside the bone tissue or the articular space) is stabilized onthe bone tissue (on a bone surface or on the edges of the joints).

The various embodiments described in the present application generallyrelate to a bone implant (1) which is in particular useful forimplantation at articular facets of two adjacent vertebrae, i.e. betweentwo facets (intra-facet implant) or through both facets (trans-facetimplants). The threading (12) is therefore particularly adapted toscrewing in bone or articular tissue.

In certain embodiments, the implant includes means for stabilization bybone attachment in proximity or at a distance from the first body (10)of the implant.

In certain of these embodiments, this stabilization by bone attachmentis achieved in proximity to the first body (10), like for example therods (21) or bells (2), rings, crowns, etc. detailed in the presentapplication with reference to FIGS. 1 to 8 and 9 to 12 . Otheradvantageous embodiments for stabilization by bone attachment inproximity to the implant are illustrated in FIGS. 29, 30, 32, 35 and 36. In certain embodiments, poly-axial locking means are provided, i.e.allowing locking of the stabilization means (generally also poly-axial)in diverse orientations. FIGS. 29 and 30 show examples of suchpoly-axial locking means (3, 26, 6). In FIGS. 29A, 29B, 29C and 29D, thestabilization means again include a ring, a crown or a bell (2) theperimeter of which may be supported on the surrounding tissues forstabilizing the implant. This bell (2) is provided with holes (24) ableto receive nails or anchors (6) having an elongated body (60) andprovided with a spike (61) allowing anchoring in the bone tissue aroundthe implant. Preferably, these nails or anchors are provided with apoly-axial head, for example by means of a shape as a sphere portion,able to cooperate with the mating shape of the holes (24) in thestabilization bell (2). Thus, it is possible to plant nails (6) alongdiverse orientations, once the bell (2) is positioned on the surroundingtissue. According to the shape of the holes (24) of the bell (2), it ispossible to provide that the nails (6) are blocked all alone by pressingagainst an abutment. Nevertheless, it is generally preferred to providean additional locking means (3), as for example illustrated in Figs, 29Cand 29D). In this example, the bell (2) is provided with an outerthreading (229) on which is screwed a locking means (3) such as a tappedring (39), able to immobilize the nails (6) or anchors in their housings(24) of the bell (2). A poly-axial stabilization element (2) is therebyobtained with additional stabilization by bone attachment, alsopoly-axial, and lockable in a poly-axial way also. The same type ofadvantage is shown in the example of FIGS. 30A, 30B, 30C, 30D and 30E.In these examples, the stabilization bell (2) is also provided withholes (24) for receiving bone attachment means (26), but the latter areformed with a crown (261) provided with teeth (265) able to be insertedthrough holes (24) of the bell (2) and to be planted in the bone aroundthe implant. This crown (261) preferably has an inner diameter greaterthan the outer diameter of the bell (2), so that poly-axiality ispreserved even after the locking. FIG. 32A shows another example of astabilization means (2) comprising a preferably cartilaginous anchoringrather than bone anchoring. In this example, the ring (2) slipped ontothe head of the implant includes at least one blade (276), preferablytwo blades, extending longitudinally and able to be anchored in thetissues around the implant. This type of embodiment is preferablyintended for interfacet implantation, i.e. with the implant positionedbetween two cartilages, but the blades are also rather intended to beinserted between both of these cartilages. Such blades may includenotches (277) opposing the withdrawal of the blades from the tissue inwhich they are planted or against which they rest. Thus, these bladeswill preferably be housed between two cartilages and their notches willstabilize them therein. In FIG. 32A, these blades are illustrated asrunning along the body of the implant at a small distance from thelatter, but of course it is possible to provide diverse spacings,notably when these stabilization means are provided for being poly-axialas detailed in the present application and as illustrated in this FIG.32A. It will be noted that such a cartilage stabilization may of coursebe achieved by means of other structures than simple blades and that itis possible to use more extended elements. On the other hand, in diverseembodiments, it is possible to provide locking means (3) by boneanchoring through the implant, as for example illustrated in FIGS. 32B,32C and 32D. In these examples, the locking means (3) include couplingmeans (31) with the implant (for example coupling by screwing) but aboveall include at least one spike (390), preferably curved, mounted on ajoint (395) of the locking means, so that during the introduction of thelocking means (3) into the implant, the spike (390) pivots around itsjoint (395) and crosses a passage (159) made in the wall of the body(10) of the implant in order to penetrate the tissue around the implant.A kind of anchor substantially transverse to the longitudinal axis ofthe implant is thereby obtained and gives the possibility of locking thelatter. It will be noted that in the case of coupling by screwing of thelocking means (3) in the body (10) of the implant, the joint (395) ofthe spike or of the spikes (390) will preferably be decoupled from therotation of the locking means, so that this joint is only move intranslation inside the implant and that the spike (390) may penetratethe surrounding tissues without any hindrance.

In certain embodiments, double poly-axiality of the stabilization meansis provided, which gives the possibility of increasing the possible tiltangle, but which also gives the possibility of either resorting or notto diverse stabilization elements combined with each other. An exampleis illustrated in FIG. 30D. For example, a first ring or crown (25), theinner wall of which at least its one portion of the sphere portion shapeof the screw head gives the possibility of providing poly-axiality. Thisfirst ring may then be used alone as a stabilization means capable ofbeing supported on the surrounding bone tissue. Further, by means of anouter wall with the shape of a sphere portion, this first ring (25) mayreceive a second ring or crown (23), the inner surface of which fits theshape of the first ring (25), thereby forming a wide stabilization means(2) than the first ring alone, allowing more extended support on thesurrounding tissues, but also allowing a greater tilt if necessary, bymeans of the double poly-axiality. The second ring (23) illustrated inthe examples of FIGS. 30C, 30D and 30E include apertures (24) forreceiving bone attachment means (26) of the type of those of FIGS. 30Aand 30B, but one skilled in the art will of course understand that anyother type of locking means or bone attachment means may be used,notably from among those (3, 6, 26, etc.) detailed in the presentapplication.

In certain of these embodiments, this stabilization by bone attachmentis achieved at a distance from the first body (10). In certain of theseembodiments, as for example illustrated in the illustrative andnon-limiting FIGS. 33A, 33B and 33C, particularly useful in the case ofan implantation of the body (10) in the interfacet space, the implantincludes a second body (8), also of an elongated shape along alongitudinal axis and substantially parallel to the first body (10).This second body (generally cylindrical or conical or frustoconical likethe first body) is preferably provided with a threading (82) adapted forbeing screwed into the bone tissue. Screwing in the cartilage is therebyobtained by the first body and screwing in one of the facets (and nolonger at the joint) or in one of the pedicles, the blades or at thebase of the spinous process by means of the second body (8). It will benoted that it is possible, like in the illustrated example, to providethat the second body (8) be also poly-axial, i.e. with a head for whichthe perimeter (88) as a sphere portion cooperates with a mating housing(58) in the plate (5), in order to allow attachment according to diverseorientations of the second body (8). In certain embodiments, the secondbody may in fact be elongated but not include any threading, such as forexample a sharpened nail or plate, nor even be rectilinear, like forexample curved anchors (2), preferably sharp (21), for example of thetype of those illustrated in FIGS. 19A, 19B, 19C, 20B, 20C or 36B and36C. It will be noted that in FIGS. 36B and 36C, a use of curved anchorsis provided with an orientation such that the curved anchoring movesaway from the first body (10) in order to provide stabilization and moreextended attachment and limiting the risks of failures of the bonestructures around the first body (10). On the other hand, in certaincases, an attachment closer to the first body (10) is preferred andcurved anchors are then used in the direction of the latter, like forexample in FIGS. 19A, 19B, 19C, 20B and 20C. It will also be noted thatit is possible to provide that the attachment at a distance by an anchor(either curved or straight) or a nail (curved or not) is achieved via apoly-axial insert positioned in the thickness of the plate (5) and ableto receive this anchor or this nail, which gives the possibility ofgiving diverse orientations to the latter. This type of solutions with asecond body allows good stabilization of the implant. Other embodimentsof stabilization means by attachment at a distance may be contemplated,such as for example a hook or a plate forming a hook, as for exampleillustrated in FIG. 34A showing a stabilization plate (5) ending with ahook (273) capable of being planted in a neighboring bone structure orbeing hooked up with a neighboring protruding bone structure. The secondbody (8) is generally positioned at a distance from the first body whichis provided for avoiding cracking or fracturing of the bone tissue bythe screwing or the implantation of both bodies. The second body is thusmaintained at a distance from the first body, preferably bystabilization means such as those described in the present application,like for example stabilization plates (5) giving the possibility ofbeing supported on the surrounding bone tissue and possibly anattachment in proximity to the first body (10) or at a distance fromthis first body (10). Diverse illustrative and non-limiting examples ofsuch plates are shown in FIGS. 19A, 19B, 19C, 20A, 20B, 20C, 31A, 31B,31C, 31D, 31E, 33A, 33B, 33C or further 34A, 34B and 34C. In particular,in diverse embodiments, the present application describes stabilizationmeans comprising rods or a bell or further plates and one skilled in theart will note that these stabilization means are mounted on the implantwith portions which generally have a thickness provided for affordinggood solidity, unlike certain implants of the prior art provided withthin plates which risk being untimely twisted or broken, as illustratedfor example in FIGS. 19A, 19B, 19C, 20A, 20B and 20C showing thickplates. On the other hand, in certain embodiments, it is possible tobenefit from thin plates capable of being twisted and thus fitting theanatomy of the implantation site. Thus, as for example illustrated inFIGS. 31A, 31B, 31C, 31D, 31E, 33A, 33B, 33C or further 34A, 34B and34C, provision may be made for deformable plates, or with shape memory,in. a plastic way in order to conform them in situ with the surroundinganatomy of the implantation site. As suggested by these figures, suchplasticity may be of course obtained by the material or by the thickness(57) of the plate (5), but also be obtained by local thinning, such asfor example grooves (271) made in the plate (5) for facilitating itsshaping by the surgeon during the implantation. In the illustrative andnon-limiting example of FIG. 34C, one benefits both from a deformableplate (5) and a non-threaded bone anchoring means, like for example ananchor or a nail to be planted through an orifice (279) made in theplate (5). In the examples of FIG. 31 , the stabilization means (5)formed by a plate (57) provided with spikes or teeth (275) adapted forbeing anchored in the surrounding bone (or cartilage) tissue, once thedefinitive shape is given to the plate (57). It will be noted that inthese examples, the screw head (further provided once more with notches(14) for receiving an implantation tool) is polyaxial, by means of asphere portion with which cooperates a hole in the plate (57) which maytherefore assume diverse orientations relatively to the implant.Further, the implant may provide, as illustrated in FIG. 31E, hooking-upmeans (13) capable of receiving attachment means (not shown) giving thepossibility of locking the position of the diverse elements of theimplant. Also, the head or the portion of the implant which is intendedto remain outside the bone tissue is generally provided so as to have arestrictive height, so as to avoid a too large protrusion (orprojection) which has the risk of damaging surrounding tissues or ofloosening the implant by the contact with other structures. Thus, bothof these types of layout are sometimes combined in certain embodimentsso that a head with a small height is provided with stabilization means,notably those provided with a second body maintained at a distance fromthe first body (10), the thickness of which represents at least onethird of the height of the protruding portion of the implants at thesurface of the bone tissue. This type of combination gives thepossibility of providing a particularly stable implant since it has ahead which is little subject to aggressions (outer aggressions) andsolidly retained by stabilization means which further protect this headfrom such aggressions. On the other hand it will be noted that in thecase of a second body maintained at a distance from the first body (10),a body provided with a head of restricted dimensions, for example with aheight not exceeding the thickness of the portion connecting both bodiestogether will be preferably selected but it is generally preferred thatthe second body have a length which is not less than 1 quarter of thatof the first body, in order to provide efficient stabilization. Finally,it will be noted that such a second body may share with the first bodyor all part of the other technical features described in the presentapplication.

The various independent but not exclusive embodiments detailed aboverepresent solutions further having the advantage of being able to beused either as a trans-facet implant, or as an inter-facet implant, forexample by the fact that the implants provides a wide space for bonegrafting in its internal conduit and/or that the bone will be sharpenedby the passage of the implant and/or that the stability of the implantis improved relatively to the known solutions.

Further, it is sometimes preferable, for better solidity, to keep asolid body at the portion on which the largest forces will be exerted,such as for is example the portion which will be finally positionedbetween the facets and/or the one where the forces transmitted throughthe stabilization means are exerted. Thus, said “at least one portion ofthe longitudinal axis” in which is made the internal conduit (11) willsometimes be a distal portion (on the side of the end opposite to thehead) or median portion, notably in the case of an intra-facetimplantation, but may also be more proximal. Nevertheless, the body maybe hollow and solid on variable portions along the longitudinal axis,for example according to the intended uses for the implant. Further, itis generally preferred that the body (10) be hollow over the whole ofits length, so that the implant may be more easily implanted by means ofa pre-positioned broach like in the known techniques of the prior artand allowing that the implant, slipped onto the broach, may slide as faras its implantation site and may then be screwed into the bone tissue(or cartilage tissue, moreover it will be noted that the terms of “bone”or “osseous” designate in the present application both the bone and thecartilage). It is therefore preferable to provide at least one passagefor such a broach, even if at least one portion not including anylongitudinal internal conduit is used. Thus, for example, FIGS. 24A and24B illustrate in an illustrative and non-limiting way an implantcomprising a hollow proximal portion, a solid median portion and ahollow distal portion, while FIGS. 25A and 25B illustrate an implant ofthe same type, but in which the median side portion however includes apassage (110) for such a broach and/or for communication between the twografting chambers provided by the two longitudinal internal conduits.The person skilled in the art will understand that various alternativesfor positioning and dimensioning the various conduits and passages arepossible. Indeed, the rigidity of the implant or of certain portions mayvary depending on the internal conduit or passage which may be, alongthe longitudinal axis, big, and then small, and then big, etc, asillustrated for example in FIGS. 16B where the two internal conduits(11) communicate through a larger passage than the one illustrated inFIG. 25B. Further, it will be noted that it is possible to make windows(15) at the portions having such a passage, as for example in FIG. 16B,or to prefer not making them as in FIG. 25B. This remains trueregardless of the size of the passage and regardless of the method formaking the windows (longitudinal or transverse machining operation),insofar that the diameter of the latter does not exceed a certain valuebeyond which it will necessarily open onto the outside of the body.Further, instead of providing a longitudinal internal conduit (11)providing a substantially cylindrical grafting chamber, as illustratedfor example in FIG. 13A and 13B, it is possible to provide conduitsand/or passages (broach and/or communication passages in particular)with a conical shape, as for example illustrated in FIGS. 14B and 15B.Such a shape has the advantage of providing a grafting chamber size anda solidity of the implant which are variable along the longitudinalaxis. Depending on the needs, it will therefore be possible to adjustthe conduits and/or passages for obtaining more or less solid portionsand/or intended to provide more or less wide grafting chambers. It willbe noted that any combinations of conduits and/or passages with aconical or frusto-conical shape with solid portions or provided with amore or less wide passage, are possible and within the scope of thepresent description.

In certain embodiments, said free end of the body (10) is self-drilling.By the term of “self-drilling” is meant here that this end is capable ofdrilling the bone tissue by itself. Such a functional definition maysimplify the application with a pointed shape of the end but may also beadvantageously obtained with a split head or by the fact that a window(15) is present on an extreme distal portion and provides a cuttingsurface giving the possibility of drilling into the bone tissue. FIGS.26B and 26C illustrate an example of a pointed free end. In thisexample, the end is solid and it is provided with a notch (112.) whichprovides a cutting edge allowing easy penetration into the bone. It willbe noted that it is possible to provide that this free end is not solid,but rather hollow, as illustrated for example in FIG. 27C where itincludes a passage (111) (narrower than the internal conduit) or forexample, because the internal conduit (11) extends as far as this distalend. On the other hand, instead of a notch on a pointed end, it ispossible to provide a notch on a cylindrical or conical orfrusto-conical end, but it is also possible to provide that the drillingfunction be obtained through at least one window (15) at the distal end.Thus, for example, a window (15) may be made, which extends over severalturns (12) and which provides a cutting edge with which the bone may besharpened more easily.

Moreover, it will be noted that in many embodiments illustrated in thefigures, the windows (15) are made between the turns (12) of thethreading and generally between the totality (and the quasi-totality) ofthe turns. However, it is possible to make these windows only on oneportion of the turns. Thus, at least one portion of said windows (15)are for example separated by at least two turns (12) without any window(15). Conversely (but not exclusively and in a way which may be combinedwith the embodiments detailed above), like for the free end, it ispossible to provide on various portions (proximal, median or distalportions), windows which extend over several turns rather than beingconfined to the space between two turns. Thus, in certain embodiments,at least one portion of said windows (15) are made on several turns(12), as for example illustrated in FIGS. 29B, 30B, 31B, 32B or 35B. Itwill be noted that it is possible to select diverse angulardistributions (radially) of these apertures or windows around thelongitudinal axis, in order to optimize the sharpening effect and/orself-filling effect during the screwing. indeed, when the windows arepresent on the areas which extend over several turns, these areas formportions where the diameter of the implant is locally reduced andoptionally allows the sharpening of the bone structures to be improvedand that the hollow implant is gradually filled with thereby sharpenedbone during the screwing, at least at the areas with a reduced diameter,as explained earlier, notably (but not exclusively) during screwingbetween two bone structures which tend to come closer to each other (atleast locally, for example on portions of a size similar to that ofthese areas with reduced diameter). Further, by distributing the windowsradially pair wise (i.e. so that a window is always diametricallyopposite to another), this effect is further increased. since thediameter is even more reduced locally. It will be noted that thisfilling of the implant with bone or cartilage may also advantageouslylimit the risk of spontaneous withdrawal of the implant, since thegrowth and bone fusion through the implant blocks the rotation andtherefore the withdrawal of the implant (or an undesired advance)

Thus, it is understood from the foregoing that various combinations ofthe features discussed in the present applications may be contemplated,such as for example a conical implant body with cylindrical threadswhich may be provided so as to enhance the bone engagement at the endand facilitate the self-filling effect, and optionally with windows ofvariable dimensions, for example, mainly greater at the end for alsopromoting the self-drilling or self-tapping aspect in this case.

As regards the turns (12) of the threading of the body, it is understoodthat they may be provided on all or part of the body, whether this isalong the longitudinal axis or around the latter. For example, portions(19) may be provided, wherein no turn/thread exceeds the perimeter ofthe body, even if windows are all the same made on these portions, suchas for example as illustrated in FIGS. 9A, 9B, 9C, 13A, 13B, 14A, 14B,15A, 15B, 16A, 16B. Further, it will be noted that these illustrativeexamples of the figures show such portions (19) at a generally proximallevel since it is there where it is less necessary to have turns deeplyanchored in the bone tissue, but various alternatives are of coursepossible. On the other hand, in certain embodiments, the turns (12) ofthe threading are “retentive”, i.e. they have a shape which promotesretention of the implant in the bone tissue. such a function may befulfilled by the fact that the turns have a face (120) facing theproximal head (the head) which is opposed to the withdrawal of theimplant, for example by the fact that this face is oriented in a planesubstantially perpendicular to the longitudinal axis, or even slightlytilted toward this proximal end, as illustrated for example in FIGS. 27Cand especially 28B. Further, in order to facilitate implantation, theother face (121) of the turns (the one facing the distal end) may on thecontrary be tilted in order to facilitate penetration, i.e. it ispreferably not parallel to the longitudinal axis but rather tiltedtowards the distal end, as illustrated for example in FIG. 28B.Nevertheless, this useful layout is not limiting and the geometry of thethread may be diverse such as for example trapezoidal, triangular, etc.

As regards the pitch of the threading, i.e. the spacing of the turnsalong the longitudinal axis, the present application also providesvarious types of non-limiting layouts which may be useful depending onthe conditions. In particular, in certain embodiments, the turns (12) ofthe thread (or by extension the thread (12) of the implant) havevariable pitch which shortens in the direction of the head (18). Also,in certain embodiment, the body (10) is provided with several threads(12) with different pitches. Preferably, the pitch of a thread locatedon the side of the free end is of a larger size than the adjacent threadlocated on the side of the head (18), so that the pitch of the thread isgradually reduced upon advancing towards the head. This type of layoutswith variable pitch gives the possibility of obtaining a compressionaleffect. Indeed, when such an implant with variable pitch or comprisingseveral threads with decreasing pitches is screwed in, a compressionaleffect is obtained which is for example particularly useful in the caseof screwing in a bone structure where it is desired to properly flattenthe structures together, like for example a trans-facet implantation.

In a general way, the implant will be inserted so that the majority ofthe body (10) penetrates into bone or cartilage tissue or between twobone structures and so that the head remains on the outside, but it ispossible to provide that the head is at least partly intended to be alsoinserted inside the treated structures. Preferably, it is provided thatthe head remains on the outside and various embodiments of the presentapplication provide in a useful way that the head bears upon (and istherefore on the outside) the surfaces. As various embodiments provideat least one internal conduit (11), it may be useful to block the latterso as to avoid bone growth risks at the surface of the treated portionsand/or invasion risks of the interior of the implant by other tissues orundesirable organisms. Thus, in certain embodiment, the said head (18)of the implant (1) closes the longitudinal internal conduit (11) orincludes means (3) for closing the longitudinal internal conduit (11).Such closing means give the possibility of providing an implant capableof being slipped onto a broach assisting the implantation like in theprior art and nevertheless allows the implant to be blocked afterimplantation. However it will be noted that various embodiments in factinclude means for stabilizing the implant, as detailed hereafter, whichgenerally include locking means which may, according to variousembodiments, fulfill this function for closing the implant.Nevertheless, in various embodiments, the locking means will be laid outso as not to block the implant so that the locking of the stabilizationmeans may be achieved in the presence of an optional broach; it willthen be possible to either provide or not closing means for blocking,according to various embodiments. Such closing or blocking means may forexample include at least one screw or a bolt mating a tapped hole in thehead, but may also include a plug provided with lugs intended to befastened with clips in an accommodation of the head, or any other meanswithin the reach of the person skilled in the art.

In certain embodiments, said head (18) of the implant (1) is providedwith means (2, 3, and 5) for stabilizing the implant, which arepreferably intended to bear upon the bone tissue around said head (18).In certain of these embodiments, said stabilization means (2, 3, 5, 6)include at least one stabilization element (2) comprising pointedstructures (21, 61, 265, 275, 276, 390), such as notches or teeth,spikes, rods or nails or anchors or further hooks, adapted forpenetrating into the bone tissue. Such stabilization means give thepossibility of an additional bone anchoring in proximity to the implant,which stabilizes the latter. For example, certain of these embodimentscomprise a stabilization element (2) forming a sort of staple comprisingat least two rods (21) substantially parallel to the longitudinal axisand able to penetrate the tissue around the head (18) and optionally aportion of said body (10) in proximity to said head (18). Examples ofsuch stabilization means (2) are for example illustrated in FIGS. 2C,3D, 7B showing elements comprising a ring intended to be slipped onto aportion of the head and at least one tip intended to be planted intosurrounding tissues, In certain of these embodiments, said rods (21) ofthe stabilization element (2) have a pointed free end. The term of“pointed” in said description in fact more widely designates the factthat a structure is able to penetrate the bone tissue, by thereforecovering, in a non-limiting way, beveled structures as well as pointedstructures. Further, in certain embodiments, said rods (21) areconnected together through a ring (23) making the stabilization element(2) able to be mounted on said head (18), as illustrated for example inFIGS. 2C, 3D, 7B, but the person skilled in the art will appreciate thatthis type of mounting on the head is only an illustrative andnon-limiting example since various layouts will give the possibility ofmounting means for the stabilization means on the head (or on any otherportion of the implants optionally). According to various alternatives,the ring (23) is slipped or screwed onto a high portion (13) which jutsout from the head (18), as illustrated for example in FIGS. 6A, 6B, 6Cand 6D, whereas, in other alternatives, the ring rests on the head andits aperture is able to receive a low portion (13) of locking means (3)which are attached in the head of the implants as illustrated forexample in FIGS. 1D or 3A, It will be noted that the figures showthreadings and tappings for attaching locking means on the head but thatvarious types of layouts are possible as detailed above with referenceto the means for closing the implant.

In certain embodiments, in particular those comprising a stabilizationelement (2) provided with two rods (21) intended to penetrate the bonetissue around said head (18), the latter includes at least two notches(14) able to receive said rods (21) or shoulders (22) positioned alongsaid rods (21) as illustrated for example in FIGS. 1A, 1B, 1C, 1D, 2A,2C, 2D, 3A, 3B, 3D, 3F or 6A, 6B, 6C, 6D, 7B and 7C. Such notches (14)give the possibility of imposing the positions of the rods (21) aroundthe implant, so that it is possible to provide that they be ideallypositioned relatively to the treated bone structures (notably so thatthey are each planted in one of the adjacent vertebrae during anintra-facet implantation). Further, the presence of a shoulder (22) (andof material between the center of the stabilization element and saidrods) allows said rods to be maintained at a distance from the body(10), so that these rods may be planted at a distance ensuring betterstabilization than if they had been closer to the body of the implant.

Further, in certain embodiments, an instrument (4) is provided for theimplantation of various embodiments of the implant (1). Such aninstrument (4) generally includes an elongated body between an end whichmay be handled by means of a handle (41) for example and an end holdingthe implant and preferably includes an internal conduit (46), asillustrated for example in FIGS. 5B and 8B, so as to be able to beslipped on around a guiding broach as detailed above. Further, in orderto facilitate implantation, such an instrument (4) may include at itsend intended to hold the implant at least one lug or protrusion (44)mating at least one notch (14) of the instrument as detailed above. Thecooperation between this lug (44) and the notch (14) allows actuation ofthe implant in rotation by the instrument so as to screw the implantinto the structures to be treated. Further, the instrument (4) sometimesincludes on the perimeter of its tubular body at least one groove (43)able to receive a piercing tool allowing the bone tissue to be pierced,into which the rods (21) of the stabilization element will be inserted.In such embodiments, the implant preferably includes a number of notches(14), double the number of rods (21) present on the stabilization means,in order to facilitate the implantation as detailed hereafter, In suchembodiments, the implants for example includes 4 notches regularlypositioned around the longitudinal axis of the implant and so that theinstrument allows the implant to be gripped with its diametricallyopposite lugs (44), while the rods (21) of the stabilization element (2)are held by the instrument and engaged into the other notches, forexample in a radial position shifted by 90° relatively to the lugs (44).Thus, it is possible by moving the instruments backward, to perform arotation by a quarter of a turn in order to bring the rods so that theyface the notches (14) via which a perforation was made in the bonetissue and to thus introduce these rods into the holes. This type oflayout facilitates the implantation by allowing preliminary piercing andby avoiding that the rods (21) interfere with the screwing of the body,for example as in the case when they would be provided to beinterdependent with the body (10) in rotation. It will be noted that theterm of “rod” is used here for designating the structures intended topenetrate into the bone tissue around the body, but it is clear that theshape of such stabilization means may vary and provision is made forrather using plates, with a. variable section and optionally T, V, H orU sections in order to provide better strengths in several dimensions.In the case of plates, it will be noted that they may be pointed orsharpened, optionally to the point of not requiring any preliminaryperforation. The instrument preferably includes means for retaining theimplants and generally a retaining element (45) for the locking means,as illustrated for example in FIGS. 5D and 8D. In these examples, theimplants include a tapped hole (31) able to receive threaded rods (13)of the locking means (3) as illustrated for example in FIGS. 1D, 2D, 3B,3C, 3F, or includes a threaded rod (13) able to receive a tapped hole(31) of the locking means (3) as illustrated for example in FIGS. 6D,7C, 8D. such a retaining means (45) may then for example include a rodintended to be flattened against the threaded rod (13) and therebyretain the assembly as illustrated in these examples of figures orinclude a threaded rod (46) (preferably tubular for the guiding broach)cooperating with a tapped hole (31) of the implant, as illustrated forexample in FIG. 18C. Further, the instrument may include, at its endretaining the implant, means for transmitting the rotation, such as forexample planar surfaces not tangent to the perimeter of the implant andcooperating with substantially identical orientation surfaces of theimplant, such as for example a nut-shaped end intended to penetrate intoa six-sided accommodation of the implant, as shown in the illustrativeexample of FIG. 17B for example. In the examples of FIGS. 6A, 6B, 6C,6D, 7A, 7B, 7C, 8A and 8B, it will be noted that the implant in factincludes a threaded rod (13) jutting out from the head (18) and providedwith a self-breakable portion, for example obtained by means of a notch(130) as for example visible in FIG. 7C. In this type of layout, thestabilization means (2) preferably include a ring (23) provided withspikes (21) as detailed earlier, but are associated with locking means(3) which may for example include a ring provided with tapping (31) ableto be screwed onto the threaded rod (13). This ring preferably alsoincludes notches (34) able to cooperate with the end of a screwing tool.On the other hand, a groove (32) may be provided on this locking means(3) in order to allow it to be fastened with clips on a lip (234) of thestabilization means, as for example visible in FIGS. 6 and 7 . Theperson skilled in the art will understand from the various technicalconsiderations above that various layouts are possible for retaining theimplant and that the means and elements above are illustrative andnon-limiting.

In certain embodiments, said stabilization means include at least onestabilization element (2) with the shape of a bell, a crown, a ring, anannulus, or any shape suitable for being mounted on (or secured to) thehead (18), preferably around at least one portion of the head. The termof “bell” is used here for referring to the mounting around the head andfor indicating that the perimeter (210) of this stabilization element isintended to be supported on the bone tissue surrounding the head (18),as for example illustrated in FIGS. 9A, 9B, 9C, 10A, 10B, 11A, 11B, etc.It is understood that the whole of the perimeter (210) of the bell isnot necessarily supported on the bone tissues all around the screw,according to the configurations, but that a support is obtained andgives the possibility of stabilizing the screw and the articularelements. In particular, diverse embodiments aim that the perimeter ofthe bell surrounds and covers a portion of the protruding bonestructures, in order to stabilize them among each other. Further, such aperimeter (210) may include teeth or notches (21) contributing to thestabilization, such as for example in FIGS. 12A, 12B and 12C In variousembodiments, the bell secured to the head is formed in a single piecewith the head or is attached above. In other embodiments, the bell ismovably mounted around the head. Further, the bell may be of the samematerial as the body of the implant (generally a solid metal material,such as for example titanium), but it is possible to provide a bell inanother notably more flexible material, so that it is crushed during thefinal screwing of the locking means and thus ensures efficientcompression. A possible and useful material for this type of alternativeembodiments is PEEK well-known in the field. Preferably, the body of theimplant is in a resistant material or at least coated with such amaterial, such as for example titanium. It will be noted that even if aresistant and durable material is generally preferred for the implant,like titanium, for example certain embodiments on the contrary providethe use of a resorbable material, for example like bone or bonesubstitute. Indeed, the use of such a resorbable material, preferablysufficiently resistant before its resorption for maintaining thetargeted attachment function, gives the possibility of obtaining finallycomplete bone fusion without any foreign body, which naturally has manyadvantages, notably for the patient.

In certain embodiments, the bell is mobile and allows a support of the“poly-axial” type, i.e. that it may be positioned against thesurrounding bone tissue, or even locked, in diverse positions relativelyto the longitudinal axis of the implant. For example, in certain ofthese embodiments, said head (18) has a peripheral lower surface (180)with the shape of a sphere portion, as illustrated for example in FIGS.18C, 22A, 22B, 22E, 22F, 23A, 23B, 23E, 28A and 28B. Such a surface isgenerally provided so as to be complementary to an internal uppersurface of said bell (2) thus jointed on the head (18) of the implant,as illustrated for example in FIG. 12C, so as to allow an adjustment ofthe orientation of the bell relatively to the axis of the head. Further,it will be noted that in such embodiments, it is preferred to use alimited sphere portion instead of a complete sphere or with too largedimensions, so that the portion of the implant which subsists at thesurface of the bone tissue is not too exposed to aggressions (notablyouter aggressions), as already detailed in the present application.Indeed, even if the range of possible orientations of the bell isthereby restricted, it remains generally sufficient and the implant willbe clearly more stable than with a large angle and especially a largerprotrusion at the surface of the bone tissue.

In certain embodiments, said bell (2) includes at least one tip or tooth(21) on its perimeter (210) for facilitating bone anchoring asillustrated for example in FIGS. 12A, 12B and 12C. This type of layoutof the low portion of the bell, intended to bear upon the bone tissue,gives the possibility of improving the adhesion of the bell on thelatter and thus improves the stability of the implant.

In certain embodiments, the bell (2), in particular when it is securedto the body (10) of the implant, includes coupling means (29) with atool for screwing the implant, such as for example illustrated in FIGS.9A, 9B, 9C, 10A, 10B and 11C. In these examples, these coupling means(29) are advantageously holes capable of receiving lugs of a screwinginstrument but the reverse configuration may be contemplated or diversecoupling means may be used. When the stabilization means are mobilearound the implant, direct coupling on the implant will of course bepreferred, like the coupling means (14) detailed in the presentapplication for example. It will be noted that these coupling means (14)of the implant may also assume diverse shapes, as specified here for thecoupling means of the bell (2).

In certain embodiments, said stabilization means include at least oneplate (5) mounted around the head (18) and provided with at least onepassage (57) able to receive a stabilization element (2), a so-calledanchor, in the form of a plate (20) able to be anchored in the bonetissue around the head (18), as illustrated for example in FIGS. 19A,19B, 19C, 20A, 20B and 20C. Like for the rods (21) described in thepresent application, the plates (20) may have diverse shapes and thisterm is not limiting, although plates are preferred to rods for thestability which they provide. Also, the plates illustrated in thefigures are not limiting and as explained for the rods, it is possibleto provide T, V, H, U plates etc. in order to provide betterstabilization (by the fact that one in fact has several plates notparallel with each other which oppose the movements in severaldirections). In certain of these embodiments, said anchor (2) includes apointed end (21) and/or sharpened edges intended to penetrate the bonetissue (pointed or sharpened designating here means for penetrating thebone). Preferably, said anchor (2) includes an end provided with atleast one abutment (22) intended to come into contact with said plate(5) and limit the penetration of the anchor (2) into the bone tissue.The anchor may generally be provided with retaining means in the bonetissue. Thus, as an addition or an alternative to such an abutment, theanchor may include catches avoiding its withdrawal out of the bone or beassociated with another locking means such as for example an additionalscrew, for which at least one portion retains the anchor. Further,according to the provided approach routes and invasivity for theimplant, it is possible to provide various shapes for such an anchor.Thus, in certain embodiments, said anchor (2) is formed with asubstantially planar plate (20), while in other embodiments, said anchor(2) is formed with a substantially curved plate (20). A combination of aflat anchor and of a curved anchor may of course be contemplater. Forbetter stability of the anchor, certain embodiments provide that saidanchor (2) and said passage (57) are laid out for inserting the anchoralong an oblique axis relatively to the longitudinal axis, so that theanchor is oriented from the center to the periphery of the implantduring the insertion, as illustrated for example in FIGS. 19A, 19B, 19C,20A, 20B and 20C. It will be noted that the illustrative examples ofthese last figures show alternatives which notably differ in that saidplate (5) is provided so as to be mounted on (or optionally secured to)the implant and for receiving the anchors which are locked by a lockingmeans (3) such as a screw or a bolt, as illustrated for example in FIGS.20A, 20B and 20C. Such a locking means added after insertion of theanchors gives the possibility of locking the assembly. On the otherhand, in the examples of FIGS. 19A, 19B and 19C, said plate (5) isseparated from the implant which is then screwed through the plate (5)receiving the anchors (2). In these examples, the locking may beobtained with the head of the implant which bears upon the anchors asillustrated for example in FIG. 19C or with an additional pin (screw orbolt) of the type of that of FIG. 20B for example.

Finally, in other embodiments illustrating the possible diversity of thestabilization means, it is possible to provide at least onestabilization element (2) in the form of a jaw comprising two curvedbits (20) each comprising a free end (21) and jointed with each otherthrough two joints (28) separated from each other by a space with a sizesubstantially equal to the size of the head (18), as illustrated forexample in FIGS. 21A, 21B and 21C. In this type of layout, the jaw maybe mounted around the head and the bits may come into contact with thebone tissues around the body (10) of the implants in order to stabilizethe assembly; in these embodiments, said stabilization means preferablyinclude locking means (3) bearing upon the stabilization element (2) formaintaining it pressed against the bone tissue. In certain of theseembodiments, the bits (20) of said jaw (2) include on their concaveface, at least one catch (211) for stabilizing them against the bonetissue. Further, in certain embodiments, the free end (21) of the bits(20) includes at least one chamfer (218) facilitating the opening of thejaw (2) upon inserting the implant into the bone tissue.

The present application describes various technical features andadvantages with reference to the figures and/ to diverse embodiments.The person skilled in the art will understand that the technicalfeatures of a given embodiment may in fact be combined with features ofanother embodiments unless the opposite is explicitly mentioned or if itis only obvious that these features are incompatible or if thecombination does not operate or does not provide solution to at leastone of the technical problems of the field, in particular thosementioned in the present application. Further, the technical featuresdescribed in a given embodiment may be isolated from the other featuresof this embodiment unless the opposite is explicitly mentioned, notablyby the functional considerations provided in the present application andthe detailed structural specificities in the description and the figuresof the present application.

It should be obvious for skilled practitioners that the presentinvention allows embodiments under many other specific forms withoutdeparting from the field of application of the invention as claimed.Therefore, the present embodiment should not be considered as anillustration but may be modified within the field defined by the scopeof the appended claims and the invention should not be limited to thedetails given above.

The invention claimed is:
 1. A bone implant comprising: a body elongatedalong a longitudinal axis between a proximal end of the body and adistal end of the body, the body comprising a rounded exterior surfaceportion disposed proximal to the first end and having a roundedcross-section transverse to the longitudinal axis; a head integrallyformed on the proximal end of the body, the head including a majordiameter larger than the rounded cross-section, the head having aperipheral lower surface that has a substantially spherical portion; abore extending through the entire body along the longitudinal axis andopening through both the proximal end and the distal end of the body; athread winding around at least a portion of the rounded exterior surfaceportion of the body; and a plurality of windows disposed along a portionof the body and forming openings between adjacent portions of the threadwinding extending from the bore and through the rounded exterior surfaceportion, each window of the plurality of windows incrementally changingin size from a proximal end to a distal end of the portion of the body,wherein a major axis of each window of the plurality of windows isincreasingly greater than a minor axis of the window from the proximalend to the distal end of the body.
 2. The bone implant of claim 1,wherein the plurality of windows incrementally increases in size fromthe proximal end to the distal end of the portion of the body.
 3. Thebone implant of claim 1, wherein each window of the plurality of windowsis flared to create at least one sharpened outer edge.
 4. The boneimplant of claim 3, wherein each window of the plurality of windows isflared from the inside to the outside of the body.
 5. The implant ofclaim 1, wherein the thread has a perimeter that is substantiallycylindrical.
 6. The implant of claim 1, wherein the plurality of windowsis aligned along an axis substantially parallel to the longitudinalaxis.
 7. The bone anchor of claim 6, wherein each window of theplurality of windows includes at least one sharpened outer edgeconfigured to penetrate bone tissue.
 8. The bone implant of claim 1,wherein a window of the plurality of windows is at least partiallyaligned with at least one of an adjacent distal window or an adjacentproximal window of the plurality of windows.
 9. A bone anchorcomprising: a body including a longitudinal axis extending from aproximal end and a distal end; a head disposed on the proximal end ofthe body, the head including a major diameter larger than across-section of the body; a bore extending through at least a portionof the body along the longitudinal axis and opening through the distalend of the body; a thread winding around the circumference of the bodyand extending from adjacent the head to the distal end; and a pluralityof windows through a sidewall of the body and extending into the bore,each window of the plurality of windows incrementally changing in sizefrom a proximal end to a distal end of the body, wherein a major axis ofeach window of the plurality of windows is increasingly greater than aminor axis of the window from the proximal end to the distal end of thebody.
 10. The bone anchor of claim 9, wherein the plurality of windowsincrementally increases in size from the proximal end to the distal endof the portion of the body.
 11. The bone anchor of claim 9, wherein eachwindow of the plurality of windows is flared to create at least onesharpened outer edge.
 12. The bone anchor of claim 11, wherein eachwindow of the plurality of windows is flared from the inside to theoutside of the body.
 13. The bone anchor of claim 9, wherein the threadhas a perimeter that is substantially cylindrical.